linux-kernel - [PATCH 2/2] ARM: dts: at91: sama7g5ek: to not touch slew-rate for SDMMC pins

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Date:   Wed, 15 Sep 2021 10:48:36 +0300
From:   Claudiu Beznea <claudiu.beznea@...rochip.com>
To:     <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <ludovic.desroches@...rochip.com>, <robh+dt@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Subject: [PATCH 2/2] ARM: dts: at91: sama7g5ek: to not touch slew-rate for SDMMC pins

With commit c709135e576b ("pinctrl: at91-pio4: add support for slew-rate")
and commit cbde6c823bfa ("pinctrl: at91-pio4: Fix slew rate disablement")
the slew-rate is enabled by default for each configured pin. The datasheet
specifies at chapter "Output Driver AC Characteristics" that HSIO
drivers (use in SDMMCx and QSPI0 peripherals), don't have a slewrate
setting but are rather calibrated against an external 1% resistor mounted
on the SDMMCx_CAL or QSPI0_CAL pins. Depending on the target signal
frequency and the external load, it is possible to adjust their target
output impedance. Thus set slew-rate = <0> for SDMMC (QSPI is not enabled
at the moment in device tree).

Fixes: 7540629e2fc7 ("ARM: dts: at91: add sama7g5 SoC DT and sama7g5-ek")
Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
---
 arch/arm/boot/dts/at91-sama7g5ek.dts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/boot/dts/at91-sama7g5ek.dts b/arch/arm/boot/dts/at91-sama7g5ek.dts
index 0bed8207d498..624162fec223 100644
--- a/arch/arm/boot/dts/at91-sama7g5ek.dts
+++ b/arch/arm/boot/dts/at91-sama7g5ek.dts
@@ -556,6 +556,7 @@ cmd_data {
 				 <PIN_PA8__SDMMC0_DAT5>,
 				 <PIN_PA9__SDMMC0_DAT6>,
 				 <PIN_PA10__SDMMC0_DAT7>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 
@@ -563,6 +564,7 @@ ck_cd_rstn_vddsel {
 			pinmux = <PIN_PA0__SDMMC0_CK>,
 				 <PIN_PA2__SDMMC0_RSTN>,
 				 <PIN_PA11__SDMMC0_DS>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 	};
@@ -574,6 +576,7 @@ cmd_data {
 				 <PIN_PC0__SDMMC1_DAT1>,
 				 <PIN_PC1__SDMMC1_DAT2>,
 				 <PIN_PC2__SDMMC1_DAT3>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 
@@ -582,6 +585,7 @@ ck_cd_rstn_vddsel {
 				 <PIN_PB28__SDMMC1_RSTN>,
 				 <PIN_PC5__SDMMC1_1V8SEL>,
 				 <PIN_PC4__SDMMC1_CD>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 	};
@@ -593,11 +597,13 @@ cmd_data {
 				 <PIN_PD6__SDMMC2_DAT1>,
 				 <PIN_PD7__SDMMC2_DAT2>,
 				 <PIN_PD8__SDMMC2_DAT3>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 
 		ck {
 			pinmux = <PIN_PD4__SDMMC2_CK>;
+			slew-rate = <0>;
 			bias-pull-up;
 		};
 	};
-- 
2.25.1